Section – A
All questions are compulsory. In case of internal choices, attempt any one of them.
1 Name the physical quantity having unit J/T.
2 Mention one use of part of electromagnetic spectrum to which a wavelength of 21 cm (emitted by hydrogen in interstellar space) belongs.
OR
Give the ratio of velocity of the two light waves of wavelengths 4000Å and 8000Å travelling in vacuum.
3 An electron with charge -e and mass m travels at a speed v in a plane perpendicular to a magnetic field of magnitude B. The electron follows a circular path of radius R. In a time, t, the electron travels halfway around the circle. What is the amount of work done by the magnetic field?
4 A solenoid with N loops of wire tightly wrapped around an iron-core is carrying an electric current I. If the current through this solenoid is reduced to half, then what change would you expect in inductance L of the solenoid.
OR
An alternating current from a source is given by i=10sin314t. What is the effective value of current and frequency of source?
5 What is the value of angular momentum of electron in the second orbit of Bohr’s model of hydrogen atom?
6 In a photoelectric experiment, the potential required to stop the ejection of electrons from cathode is 4V. What is the value of maximum kinetic energy of emitted Photoelectrons?
7 In decay of free neutron, name the elementary particle emitted along with proton and electron in nuclear reaction.
OR
In the following nuclear reaction, Identify unknown labelled X.
8 How does the width of a depletion region of a pn junction vary if doping concentration is increased?
OR
In half wave rectification, what is the output frequency if input frequency is 25 Hz.
9 When a voltage drop across a pn junction diode is increased from 0.70 V to 0.71V, the change in the diode current is 10 mA .What is the dynamic resistance of diode?
10 Which specially fabricated pn junction diode is used for detecting light intensity?
For question numbers 11, 12, 13 and 14, two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
a) Both A and R are true and R is the correct explanation of A
b) Both A and R are true but R is NOT the correct explanation of A
c) A is true but R is false
d) A is false and R is also false
11 Assertion(A) :
In a nonuniform electric field, a dipole will have translatory as well as rotatory motion.
Reason(R):
In a nonuniform electric field, a dipole experiences a force as well as torque.
12 Assertion(A):
Electric field is always normal to equipotential surfaces and along the direction of decreasing order of potential
Reason(R):
Negative gradient of electric potential is electric field.
13 Assertion (A):
A convex mirror cannot form real images.
Reason (R):
Convex mirror converges the parallel rays that are incident on it.
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